When I attempt to open an app originally made for os9, I get an error: "You can't open the application "Pedigree/Draw" because the Classic environment is no longer supported." How do I get past this? Can I boot in an os9 mode?
if your Mac shipped with it, you could install OS X 10.4, the last OS X to support the +Classic environment+, on an external drive and boot from there.
MacBooks cannot run OS9, not even running from an external drive.
What Application are you trying to use? Chances are good that in the decade since OS9 was discontinued, the developer has made an OS X-native version of the application.
Note, only 2002 and earlier Macs can guarantee booting into Mac OS 9. The only exception being the non-Firewire 800 PowerMac G4 whose rear lacks the Firewire 800 port shown here: